1. Field of the Invention
The present invention relates to novel aqueous dispersions based on a silicone and an organic polymer latex, such novel aqueous dispersions being crosslinkable into elastomeric state upon removal of water therefrom.
2. Description of the Prior Art
Silicone-based aqueous dispersions crosslinkable into elastomeric state on removal of water therefrom are known to this art. These comprise:
(a) an emulsion (A) of the oil-in-water type of an .alpha.,.omega.-(dihydroxy)polydiorganosiloxane, stabilized with an anionic and/or nonionic surfactant; PA1 (b) a crosslinking agent; PA1 (c) a nonsiliceous inorganic filler; and PA1 (d) a curing catalyst. PA1 (i) colloidal silica (U.S. Pat. Nos. 3,294,725 and 4,221,688); PA1 (ii) sodium silicate (U.S. Pat. No. 4,244.849); PA1 (iii) an amorphous silica powder (FR-A-2,463,163); PA1 (iv) a microemulsion of a silsesquioxane resin (U.S. Pat. No. 3,355,406); PA1 (v) a siliconate (EP-A-266,729, EP-A-332,544 and EP Application 89/4,200,567, filed Feb. 16, 1989 and assigned to the assignee hereof); PA1 (vi) a reactive silicone resin of low molecular weight, containing alkoxy or acyloxy groups (U.S. Pat. No. 4,554,1870; PA1 (vii) a silicone resin of high molecular weight, insoluble in toluene (EP-A-304,719); PA1 (viii) a polyalkoxysilane, a polysilicate, a polyacyloxysilane or a polyketiminoxysilane (U.S. Pat. Nos. 3,294,725, 4,584,341, 4,618,642 and 4,608,412); PA1 (ix) a polyamino- (or amido)silane (Application FR-A-89/01,654, filed Feb. 3, 1989 and assigned to the assignee hereof); PA1 (x) a polyalkenoxysilane (Application FR-A-88/13,618, filed Oct. 11, 1988 and assigned to the assignee hereof); PA1 (xi) a hydroxylated silicone resin containing, per molecule, at least two siloxy units selected from among those of the formulae: R.sub.3 SiO.sub.0.5 (M), R.sub.2 SiO (D), RSiO.sub.1.5 (T) and SiO.sub.2 (Q) (Application FR-A-88/11,609, filed Aug. 31, 1988 and also assigned to the assignee hereof). PA1 (1) Insufficient storage stability; PA1 (2) Mediocre adhesiveness to many substrates, in particular those employed in the construction industry (glass, concrete, metals, steel, aluminum, thick plastic coatings such as PVC, limestone, and the like); PA1 (3) Paints prepared from these aqueous dispersions exhibit a binding power and a resistance to abrasion, in particular to wet abrasion, which may be insufficient; PA1 (4) Elastomers produced from these aqueous dispersions on evaporation of water exhibit a very high shrinkage, associated with a modulus of elasticity (ME) and a tearing strength (TrS) which are too low for certain applications; PA1 (5) Excessively high viscosity of silicone emulsions having high solids contents which are required for formulating filled aqueous dispersions of low volume extract. PA1 (1') The coating formed exhibits an insufficient permeability to gases and in particular to water vapor; PA1 (2') The viscosity of the aqueous dispersion is too low and its film-forming capacity may be insufficient; PA1 (3') The coatings obtained are too water-sensitive and insufficiently water-repellent; PA1 (4') The coatings obtained are sensitive to actinic radiation and in particular to UV. PA1 FR-A-2,526,033 and U.S. Pat. Nos. 4,012,355 and 2,739,910 describe the combination of a siliconate and an organic polymer latex; PA1 DE-A-2,355,813 describes a system in which the siliconate may be replaced by a silicone resin emulsion; according to CH-A-61,842 both the siliconate and a silicone resin are associated with an acrylic acid copolymerizate. PA1 (i) a core of crosslinked silicone rubber; PA1 (ii) a first sheath of crosslinked acrylic rubber; and PA1 (iii) a second sheath obtained by radical (co)polymerization of resin-forming monomers. PA1 (1) A storage stability of at least six months, preferably at least one year; PA1 (2) A viscosity of the unfilled material and of the material packaged in a cartridge which is suitable even in the event of aqueous dispersions which have a high solids content of more than 75%, these dispersions producing elastomers of relatively low modulus; PA1 (3) A satisfactory adhesiveness to the widest variety of substrates, e.g., stone, concrete, mortar, metals, steel, aluminum, fibro-cement, enamels, ceramics and plastics such as PVC; PA1 (4) A suitable viscosity, endowing them with an extrudability from the packaging cartridge and a suitable film-forming capacity; PA1 (5) A suitable resistance to abrasion, in particular to wet abrasion, to atmospheric moisture and to actinic radiations (visible light, UV); PA1 (6) Good permeability to gases and to water vapor; PA1 (7) Satisfactory mechanical properties, in particular as regards modulus of elasticity and tear strength; PA1 (8) A satisfactory water-repellency. PA1 (A) 100 parts of an oil-in-water emulsion of an .alpha.,.omega.-(dihydroxy)polydiorganosiloxane, stabilized with at least one surface-active agent selected from among the anionic and nonionic surface-active agents and mixtures thereof; PA1 (B) 2 to 80, preferably 3 to 40, parts of an aqueous dispersion of an organic (co)polymer which has a particle size ranging from 0.07 to 0.5 .mu.m, preferably from 0.05 to 0.2 .mu.m, and a solids content ranging from 20% to 70% by weight; PA1 (C) an effective amount of at least one crosslinking agent; PA1 (D) 5 to 200, preferably 50 to 150, parts of a nonsiliceous inorganic filler; PA1 (E) optionally, 0.01 to 3 parts by weight of a metal curing catalyst, PA1 (a) Alkyl (meth)acrylates, the alkyl moiety of which preferably has from 1 to 18 carbon atoms, in particular methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, amyl acrylate, lauryl acrylate, isoamyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, methyl methacrylate, chloroethyl methacrylate, butyl methacrylate, 3,3-dimethylbutyl methacrylate, ethyl methacrylate, isobutyl methacrylate, isopropyl methacrylate, phenyl methacrylate, butyl chloroacrylate, methyl chloroacrylate, ethyl chloroacrylate, isopropyl chloroacrylate and cyclohexyl chloroacrylate; PA1 (b) .alpha.,.beta.-Ethylenically unsaturated esters of monocarboxylic acids, the acidic moiety of which is nonpolymerizable and the unsaturated moiety preferably has from 2 to 14 carbon atoms and the acidic moiety from 2 to 12 carbon atoms, in particular vinyl acetate, vinyl propionate, vinyl butyrate, allyl acetate, vinyl versatate.RTM. (registered trademark for esters of C.sub.9 -C.sub.11 .alpha.-branched acids), vinyl laurate, vinyl benzoate, vinyl trimethylacetate, vinyl pivalate and vinyl trichloroacetate; PA1 (c) The esters and half-esters of .alpha.,.beta.-ethylenically unsaturated polycarboxylic acids having from 4 to 24 carbon atoms, in particular dimethyl fumarate, diethyl maleate, methyl ethyl fumarate and 2-ethylhexyl fumarate; PA1 (d) Vinyl halides, in particular vinyl chloride, vinyl fluoride, vinylidene chloride and vinylidene fluoride; PA1 (e) Vinylaromatic compounds preferably having not more than 24 carbon atoms and selected in particular from among styrene, .alpha.-methylstyrene, 4-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methoxystyrene, 2-hydroxymethylstyrene, 4-ethylstyrene, 4-ethoxystyrene, 3,4-dimethylstyrene, 2-chlorostyrene, 3-chlorostyrene, 4-chloro-3-methylstyrene, 4-tert-butylstyrene, 4-dichlorostyrene, 2,6-dichlorostyrene, 2,5-difluorostyrene and 1-vinylnaphthalene. PA1 (f) Conjugated aliphatic dienes preferably having from 3 to 12 carbon atoms, in particular 1,3-butadiene, isoprene and 2-chloro-1,3-butadiene; PA1 (g) .alpha.,.beta.-ethylenically unsaturated nitriles preferably having from 3 to 6 carbon atoms, such as acrylonitrile and methacrylonitrile. PA1 (i) of a monomer (a) and of a monomer (b), such as copolymers of the vinyl acetate/alkyl acrylate type; PA1 (ii) of a monomer (a), of a monomer (b) and of a monomer (c), such as, for example, a terpolymer of the acetate/acrylate/maleate type; PA1 (iii) of a monomer (b), of a monomer (d) and of an olefinic monomer, such as, for example, the acetate/vinyl chloride/ethylene terpolymer; PA1 (iv) of a monomer (e) and of a monomer (a), among which styrene/alkyl acrylate copolymers in which the styrene/alkyl acrylate weight ratio ranges from 30/70 to 70/30 are very particularly representative; PA1 (v) of a monomer (e) and of an .alpha.,.beta.-ethylenically unsaturated carboxylic acid preferably having from 4 to 12 carbon atoms, including mono- and polycarboxylic acids such as (meth)acrylic acids, itaconic acid, maleic acid, fumaric acid, such as the styrene/methacrylic acid copolymer; PA1 (vi) of a monomer (e), of an .alpha.,.beta.-ethylenically unsaturated carboxylic acid indicated above and of a monomer (g), such as the styrene/acrylonitrile/itaconic acid copolymers; PA1 (vii) of a monomer (e) and of a monomer (f). PA1 (1) an .alpha.,.beta.-ethylenically unsaturated carboxylic acid monomer indicated above, including mono- and polycarboxylic acids (acrylic, methacrylic, maleic, itaconic, fumaric and similar acids); PA1 (2) an ethylenic monomer containing secondary, tertiary or quaternized amine groups (vinylpyridines, diethylaminoethyl methacrylate, etc.); PA1 (3) a sulfonated ethylenic monomer (vinyl sulfonate, styrenesulfonate, etc.); PA1 (4) a zwitterionic ethylenic monomer (sulfopropyl(dimethylaminopropyl) acrylate); or nonionic in character, in particular: PA1 (5) amides of unsaturated carboxylic acids (acrylamide, methacrylamide, etc.); PA1 (6) esters of (meth)acrylates and of polyhydroxypropyl or polyhydroxyethylated alcohols. PA1 (i) a "twin population" particle size distribution, namely, a first population of particles preferably originating essentially from the dispersion (B) whose particle size ranges from approximately 0.01 .mu.m to 0.15 .mu.m, preferably 0.10 .mu.m, and a second population of particles originating preferably essentially from the emulsion (A) and exhibiting a particle size ranging from 0.15 .mu.m to 100 .mu.m, generally from 0.20 .mu.m to 5 .mu.m; PA1 (ii) a solids content of more than 60% by weight, preferably more than 70% by weight; PA1 (iii) a viscosity of less than 50,000 mPa.s at 25.degree. C., measured at a shear rate of 1 s.sup.-1, prior to the incorporation of the fillers (D), such as to provide a final dispersion which can easily be extruded from the storage cartridge. PA1 (i) 0.1 to 10 parts of colloidal silica; PA1 (ii) 0.5 to 10 parts of sodium silicate; PA1 (iii) 1 to 15 parts of silica powder selected from pyrogenic or fumed silicas and precipitated silicas; PA1 (iv) 0.1 to 15 parts, preferably 1 to 10 parts of an organosiliconate; PA1 (v) 1 to 100 parts of a silsesquioxane resign microemulsion according to the combined teachings of U.S. Pat. Nos. 3,355,406 and 3,433,780; PA1 (vi) 5 to 100 parts of a reactive silicone resin of low molecular weight, containing alkoxy and acyloxy groups; PA1 (vii) 5 to 100 parts of a silicone resin of high molecular weight, insoluble in toluene; PA1 (viii) 5 to 100 parts of a hydroxylated silicone resin containing, per molecule, at least 2 different units selected from those of the formulae: R.sub.3 SiO.sub.0.5 (M), R.sub.2 SiO (D), RSiO.sub.1.5 (T) and SiO.sub.2 (Q), R preferably being a C.sub.1 -C.sub.6 alkyl, vinyl and 3,3,3-trifluoropropyl radical, and having a weight content of hydroxyl groups of from 0.1% to 10%; among these resins, which are introduced as such or in the form of aqueous emulsions, representative are MQ, MDQ, TD and MTD resins; PA1 (ix) 1 to 20 parts of a silane of the formula: EQU R.sub.a SiX.sub.4-a
The base emulsion contains a reactive silicone oil having silanol endgroups, which is generally polymerized in emulsion according to the technique described in U.S. Pat. Nos. 2,891,920, 3,294,725 and 3,360,491, namely, using an anionic surfactant which preferably also serves as the polymerization catalyst.
EP-A-327,321 describes an aqueous dispersion of the above type, in which the base emulsion is a mixture of a macroemulsion of a reactive silicone oil and a microemulsion of a reactive silicone oil having a particle size of less than 0.14 .mu.m. A dispersion of this type presents the twin disadvantage of being costly and of crosslinking on evaporation of water into an elastomer exhibiting insufficient adhesiveness to substrates and/or mediocre mechanical properties.
In this general type of aqueous dispersion that crosslinks into elastomeric state on removal of water, the literature indicates the option of using a wide variety of crosslinking agents for the base emulsion, among which are:
These aqueous dispersions are typically catalyzed using a curing catalyst which is, preferably, a tin salt, and which may also be the combination of a tin salt and boric acid (U.S. Pat. No. 4,863,985).
However, these aqueous dispersions present many disadvantages, the most notable of which being:
Furthermore, organic (co)polymer latex aqueous dispersions, for example of alkyl (meth)acrylate and of vinyl esters of monocarboxylic acids, have long been used as paints to provide thin coatings or thick coatings, in particular in the construction industry for waterproofing facades and roofing.
These aqueous dispersions typically present the following disadvantages:
The patent literature has also described the combination of a silicone and an organic latex;
None of these documents describes the further use of an emulsion of a silicone oil having silanol endgroups, of nonsiliceous filler and of curing catalysts.
EP-A-246,537 describes the preparation, in latex form, of a laminated elastomeric material of the following three elements: